Conventionally, the tip (cutting insert) described in Japanese Unexamined Patent Application Publication No. 2001-212704A (Patent Document 1) has been known as a cutting insert used in grooving of a work material. In the tip described in Patent Document 1, a front cutting edge is formed along a ridge line of a rake surface (top surface) and a front relief surface (front side surface). At substantially the center of the cutting edge ridge of the front cutting edge, a recess portion is disposed and lowers the rake surface, and a recessed groove extending successively rearward from the recess portion is disposed on the rake surface.
The front side surface on the tip described in Patent Document 1 is inclined rearward as it goes downward due to the fact that it is a relief surface. For this reason, the recess portion is formed recessing downward in a front end view, and formed recessing rearward in a top view. As a result, in grooving of a work material, an unmachined portion may be left at the groove bottom which is the machined surface, and smoothness of the groove bottom decreases.
In light of the problems described above, an object of the present aspect is to provide a cutting insert that can form a groove bottom with good machining precision, a cutting tool, and a method for manufacturing a machined product.